The present invention relates to a contrarotating propeller type propulsion system used on aircraft particularly concerned with a planetary drive design wherein a planetary gear is interposed between a sun gear fixed to a driving shaft and a ring gear concentrically surrounding and rotating on its axis around the sun gear. A first output rotary cylinder for driving a first propeller is coupled to the ring gear and a second output rotary cylinder for driving a second propeller is coupled to a support shaft for the planetary gear. Such a contrarotating propeller type propulsion system is disclosed in, for example, Japanese Patent Laid-Open No. 139598/1985 and U.S. Pat. Nos. 4,563,129 and 4,842,484.
In the construction of such a propulsion system, usually the output rotary cylinder is supported on a stationary support structure which is used to carry thereon another output rotary cylinder through bearing means. A large relative rotational speed is generated between the first and second output rotary cylinders rotating in opposite directions which affects the bearing means, thus accelerating wear on the bearing means.
Moreover, in a contrarotating propeller type propulsion system of this type in which the driving shaft is driven by a turbine supplied with hot exhaust gases from a gas propulsion apparatus, the hot exhaust gases are circulated in close proximity to the planetary drive system and may further accelerate the wear on the various components.